The fund, the Libyan Investment Authority, says in the suit it estimates Goldman made $350 million in profits on $1 billion in trades.

The suit was filed last week, but details of the Libyan fund's claims were made available on Thursday.

The lawsuit claims Goldman took advantage of its relationship with the Libyan fund, dating to 2007, to gain its managers' "trust and confidence," resulting in large investments and "inadequately documented" trades.

The resulting series of 2008 equity-derivatives trades handled by Goldman, and amounting to more than $1 billion, expired worthless in 2011, according to the Libyan Investment Authority's lawsuit, which seeks recovery of losses from the trades.

"We think the claims are without merit, and we will defend them vigorously," a Goldman spokeswoman said.

-- Write to Liz Rappaport at liz.rappaport@wsj.com and Jenny Strasburg at jenny.strasburg@wsj.com